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  • Dr. Stephanie Bayliss ND

Vitamin B12 and Brain Health

If you are presenting with concerns related to mental health, cognitive decline or symptoms of a neurological origin, I will be investigating the status of your B12. Let me explain why …

B12 and the Neurological System

B12 is the cofactor for the synthesis of methionine; a crucial amino acid that is the foundation of the one-carbon cycle, which generates methyl groups for the synthesis of neurotransmitters, myelin, DNA and RNA. Neurotransmitters are important for neurons (brain cells) to communicate and can become dysregulated for a number of reasons. Examples of neurotransmitters include serotonin (implicated in depression), dopamine (implicated in Parkinson's disease), as well as norepinephrine and epinephrine. Myelin is the sheath that protects all the nerves within our body. It facilitates efficient transformation of signals along our neurons.

Given B12’s foundational role in synthesizing neurotransmitters and myelin, chronic deficiency can result in a diversity of neurological symptoms. A good example of this is a published case study of psychiatric symptoms manifesting as a B12 deficiency. 1

B12 is also important as a cofactor in transitioning homocysteine to the aforementioned methionine through the methylcycle. Elevated levels of homocysteine can therefore be indicative of deficiencies in B vitamins. Elevated levels of homocysteine have also been implicated in all forms of cardiovascular disease, dementia, ischemic strokes and problems associated with pregnancy including neural tube defects and preeclampsia. 2

Further evidence demonstrates B vitamins’ effectiveness in slowing brain atrophy in a population with mild cognitive impairment and Alzheimer's disease. 3

Prevalence of deficiency

Deficiencies in B12 can manifest due to decreased absorption primarily from achlorhydria (also known as decreased stomach acid), which can occur for a whole host of reasons including:

  • The natural aging process

  • Proton pump inhibitors

  • Chronic stress

  • Other medications

Dietary sources of B12 are limited primarily to animal proteins, but include other sources such as certain seaweeds and algaes, as well as nutritional yeast. For an in depth look at B12 content of individual foods, the dieticians of Canada have done an excellent job outlining this.

Unfortunately, the high usage rates of proton pump inhibitors, especially in the elderly population, also correlates to an increase in vitamin B12 deficiency, as these acid suppressors inhibit the absorption of B12. Given that this population is especially at risk for cognitive decline, it is important that people understand the risks. As is represented in this study, 16.2% of people taking a proton pump inhibitor or H2 blocker had a vitamin B12 deficiency.4 Additionally, increased doses of PPIs or H2 blockers correlated to higher rates of B12 deficiency. If you are on a proton pump inhibitor it is of utmost importance that you are supplementing with Vitamin B12 to offset the decreased absorption of B12.

As an aside - there are many naturopathic alternatives to treating gastroesophageal reflux disease, also commonly known as indigestion.


  • Testing B12 involves a simple blood test that can be completed at Lifelabs through your primary care doctor. The reference range is wide - as Naturopathic Doctors, we prefer to see B12 well above 450 pmol/L.

  • Homocysteine is a fasting blood test that also can be completed at Lifelabs. Total homocysteine is ideal under 13 umol/L.

Supporting Deficiencies

Oral absorption of B12 is minimal - it is best absorbed through intramuscular injections. Not all forms of vitamin B12 are alike.

  • Cyano-cobalamin is a synthetic form of B12 which contains a cyanide group that is not naturally occurring in your body. In our office at Acacia, we use varying strengths of methylcobalamin for our B12 injections. I will often times recommend patients cease any form of supplementing cyanocobalamin, as it can be harmful in patients with MTHFR gene mutations (which over 50% of the population has).

  • Dr. Ben Lynch has dedicated his career to educating patients on this relationship. More information can be found by clicking on this link.

  • Other safe and absorbable forms of B12 include hydroxy or adenosyl-cobalamin.


  1. Berry, N., R. Sagar, and B. M. Tripathi. "Catatonia and other psychiatric symptoms with vitamin B12 deficiency." Acta Psychiatrica Scandinavica108.2 (2003): 156-159.

  2. Ganguly, Paul, and Sreyoshi Fatima Alam. "Role of homocysteine in the development of cardiovascular disease." Nutrition journal 14.1 (2015): 1.

  3. Smith, A. David, et al. "Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial." PloS one 5.9 (2010): e12244.

  4. Lam, Jameson R., et al. "Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency." Jama 310.22 (2013): 2435-2442.

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